Experimental Carbonation Study for a Durability Assessment of Novel Cementitious Materials.

Lucija Hanžič,Aljoša Šajna,Marie Helene Bjørndal,Yushan Gu,Benoît Bary,Rosa Maria Lample Carreras,Alisa Machner,Klaartje De Weerdt,Sebastijan Robič

doi:10.3390/ma14216253

Abstract

Durability predictions of concrete structures are derived from experience-based requirements and descriptive exposure classes. To support durability predictions, a numerical model related to the carbonation resistance of concrete was developed. The model couples the rate of carbonation with the drying rate. This paper presents the accelerated carbonation and moisture transport experiments performed to calibrate and verify the numerical model. They were conducted on mortars with a water-cement ratio of either 0.6 or 0.5, incorporating either a novel cement CEM II/C (S-LL) (EnM group) or commercially available CEM II/A-S cement (RefM group). The carbonation rate was determined by visual assessment and thermogravimetric analysis (TGA). Moisture transport experiments, consisting of drying and resaturation, utilized the gravimetric method. Higher carbonation rates expressed in mm/day−0.5 were found in the EnM group than in the RefM group. However, the TGA showed that the initial portlandite (CH) content was lower in the EnM than in the RefM, which could explain the difference in carbonation rates. The resaturation experiments indicate an increase in the suction porosity in the carbonated specimens compared to the non-carbonated specimens. The study concludes that low clinker content causes lower resistance to carbonation, since less CH is available in the surface layers; thus, the carbonation front progresses more rapidly towards the core.

Highlights

The design process of concrete structures relies on standards such as Eurocode 2 [1,2]and guidelines such as fib Model Code 2010 [3]
This study aims to present the experimental results of an accelerated carbonation program conducted on mortar specimens incorporating a novel CEM II/C (S-LL) binder developed within the EnDurCrete project [5], and to compare it with the performance of mortars prepared with commercially available cement, CEM II/A-S
Carbonation Rate plotted as a function of the depth from the exposed surface

Summary

Introduction

The design process of concrete structures relies on standards such as Eurocode 2 [1,2]. Guidelines such as fib Model Code 2010 [3]. The main focus of the existing codes and guidelines is on mechanical performance, which is analyzed with advanced structural design models. Durability-related phenomena are addressed mainly through the selection of exposure classes and experience-based requirements. Concrete durability forecasts are only crude approximations, which are not supported by the sophisticated modelling of concrete degradation over time. The deterioration and maintenance of concrete are having a significant impact on public sector budgets. Maintenance costs and shutdowns of infrastructure, such as tunnels, bridges or power plants, are important, due to their impact on the wider community

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